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DCT-Domain Blind Measurement of Blocking Artifacts

DCT-Domain Blind Measurement of Blocking Artifacts. Model Blocking Artifacts as a 2-D Step Function in b Parameters are Computed in the DCT Domain HVS Based Measurement Activity masking Luminance masking. : the magnitude of s. : the background luminance. : the activity inside b.

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DCT-Domain Blind Measurement of Blocking Artifacts

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  1. DCT-Domain Blind Measurement of Blocking Artifacts • Model Blocking Artifacts as a 2-D Step Function in b • Parameters are Computed in the DCT Domain • HVS Based Measurement • Activity masking • Luminance masking : the magnitude of s : the background luminance : the activity inside b Side view of the 2-D step function s

  2. Experimental Results Lena JPEG-coded at 0.22 bits/pixel Lena JPEG-coded at 1 bits/pixel

  3. Experimental Results cont. • Global Measure of Blocking Artifacts • Consistent with Other Methods [Wang , Evans & Bovik, 00], [Coudoux, Gzalet & Corlay 98] [Coudoux, Gzalet & Corlay 98] , N : the total number of inter-block boundaries. : local measure of blocking artifact at each inter-block boundary k : # of block boundary S. Liu, and A. C. Bovik, “DCT-Domain Blind Measurement of Blocking Artifacts in DCT-coded Images ”, ICASSP 2001.

  4. DCT-Domain Reduction of Blocking Artifacts • Edge Detection in the DC Image • Sobel gradient operator • All Block Boundaries are Divided into Three Categories • Type I: • Type II: and neither of the two adjacent blocks is edge block • Type III: and at least one of the two adjacent blocks is edge block : measured visibility of blocking artifact : threshold of visible blocking artifacts Edge block: block on the detected edges

  5. DCT-Domain Reduction of Blocking Artifacts cont. • No Process for Type I Block Boundaries • Replace the 2-D Step Function with a 2-D Linear Function for Type II Block Boundaries • Post-filtering Type II and Type III Block Boundaries in the DCT Domain for (k,l)=(0,0) , , otherwise

  6. Performance and Comparison • The Proposed Method Has Good Performance • Improves image visual quality significantly • Low computational cost, less than 30% of the method proposed in [Chen, Wu & Qiu 01] JPEG-coded Lena S. Liu, and A. C. Bovik, “EfficientDCT-Domain Blind Measurement and Reduction of Blocking Artifacts ”, IEEE Trans. On Circuits and Systems for Video Technology, submitted

  7. Decoded Image DCT-domain zeroing method [zeng, 99] DCT-domain postfiltering[chen et al, 01] Proposed method

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